Can Digital Presses Really Maintain Consistency?

Recently, a Chetan Karia, co-founder of Printbook in Mumbai, India, posed a question in a LinkedIn group that ignited impassioned debate. He asked, “Is there any printing press or digital printer that will print the same thing over and over (couple thousand sheets a day) and maintain its color consistency?” With nearly 100 responses in a matter of days, there was no doubt that he’d tapped into a hotbed of emotion.

First to respond was Toronto-based Erik Nikkanen, a mechanical engineer and researcher in printing theory and technology development. He pointed out that all printing processes have inherent variation because they involve mechanical parts.

“All printing processes are analogue, and that even goes for what people call digital printing processes,” he wrote. “The process of transferring an ink or other colorant to a substrate is a physical process, not a digital process. For example, with inkjet, the consistency of the transfer of ink depends on the consistency of the jetting of the ink from the nozzle, the consistency of the mechanical/electrical components that drive it, and how the colorant interacts with the substrate. Digital information does not have variation, but physical systems do.”

While all systems have variation, Nikken said, the question is really whether a printer can find a system that has a low enough level of variation to satisfy their needs. He then talked about the differences between passive and forced systems for ink application and how that would affect the results.

“A forced system has much more potential to meet your desired performance goal than any passive system, but the consistency of the forced positive ink feed systems still require that they are designed properly,” he said. “Digital printing systems can be improved, and I am sure that is what engineers are looking into.”

Many of the participants added their own experiences with different machines and their consistency and repeatability.

“The closest I've seen in a toner machine was a small device made by Once that used six opaque toners that were only applied in a single layer—no two colors ever overlaid each other,” said Paul Gardner, director of innovation for Hudson Printing (Salt Lake City). “I watched a group of six of those machines print nearly identical color across two days and many thousand sheets at a demo in Poing. The second closest I've seen are the HP T-series inkjet presses.”

Nikola Ristic, service engineer at 3 Print (Slovenia), seconded Gardner’s comment. “Yes, of course. The HP Indigo 6x00 digital press using the Esko workflow and the Continuous Color Calibration (CCC) feature.”

Some focused on ICC profiles, while others argued that the only way to get the desired consistency is good maintenance practices and having high-quality linearization devices.

Reeve Schragger, prepress manager at Doculink Australia (Port Melbourne), jumped in to share his experience as running the first ever successful ISO color calibration of a digital press using an HP Indigo press.

“Part of the test required running a set of 50,000 impressions of a test sheet that included photos and a spectrophotometer swatch,” he writes. “These sheets were sent to Switzerland and checked, and were all within three delta E so we got the accreditation.”

However, this was based on a very stable stock and the specification required that they recalibrate the machine often, which added to the cost. “So it is by no means a solution to all problems, just an example of what is possible,” Schragger concluded.

This raised the issue of profitability. Repeatability within a certain tolerance is certainly possible, but is it profitable?

“One can discuss this fascinating topic at exhaustive length, as has been shown,” contributed Mike Lucey, digital workflow consultant at Diarmid Lucey (Albany, NY). “However, a practical answer is that, yes, color consistency can be held to a ‘good enough’ tolerance on any one of several digital presses if (a) you can control your environment—temperature, humidity, etc.—and your paper stock and (b) you develop trained, diligent operators who calibrate carefully and keep the press(es) in top condition. It is a separate question as to whether one can do this and still make a reasonable profit.”

Daniel Woodward, business development manager at Canon Australia, agreed that process is critical. “A base line ‘test chart’ calibration needs to be set and referenced against future calibrations (on the same media). This should be done on install. If you don't know where the printer needs to be, just calibrating and hoping for best does not tend to work. Have a look at the new presses from Canon, Xerox, and Konica Minolta. Things have come along way in this area, as have RIP options for calibrating media families.”

Others threw their hats into the ring when it came to favorite presses, as well. There was also discussion about whether the toner is more consistent than high-speed inkjet, as well as the role of the substrate, printing speed, and ink coverage in achieving consistency.

But as Daniel Dickinson, digital print manager at Precision Services Group (Tustin, CA), pointed out, “Every digital press manufacture is going to say they offer great color consistency, but that's not true. We have two Kodak NexPresses and we get a lot of work because customers are unhappy with the color consistency at other printing companies, but they're very happy with us.”

Gary Hayes, managing director at Fotocopy Design & Print (New Zealand), adds that when it comes to profitability, it’s important to remember that customers don’t always see things the way printers do.

“Given that not everything can be held totally consistent (variation in media, environment, power fluctuations, toner/ ink batches, wear and tear on equipment, etc.), there will always be variation,” he says. “Whether it is detectable by the customer's eye is another matter. Calibration certainly helps, but only to a point.”

Hayes recalled how he used to go to “ludicrous” lengths to match colors simply because customers said they wanted him to. But now he gives a reality check first.

“As I have children and staff that need the occasional meal, we hold the equipment at a ‘decent’ level of consistency and calibration and do the odd tweak to give a ‘good’ result,” he explains. “I have had a very few customers over the past few years say could I get it closer, and I say, ‘Probably, but it can get expensive to match more accurately than this as we have to go through quite lengthy tests.’ I explain very briefly why color varies in printing and that the same problem will exist, to a greater or lesser extent, wherever they get their printing done. Once the cost of precise color matching is put back on their shoulders, it suddenly does not seem quite as vital. I can't recall anyone saying, ‘Go ahead charge me heaps more because I must have the color exact.’ Everyone has said it would be all right, don't worry about it. Of course, I am talking about small, usually quite subtle variations, but the point is that everything is relative, and if the customer values the difference they should be happy to pay.”

SHOTZ Print (Australia) argued that not only is digital print consistency achievable (defined as within a very tight set of tolerances), but it is reasonably achievable.

“My current digital press, a Xerox 800, has on-board calibration, which makes on-the-fly adjustments to ensure color consistency across the sheet and throughout the run. Outside of that calibration, we also calibrate the RIP to the print engine daily, and if a particularly sensitive color is involved, we will even re-calibrate for the job. This gives us not only day to day consistency, but year on year consistency. Although my experience is purely Xerox, I have no doubt that most—if not all—serious digital print engines today are capable of the same ‘yes’ answer in the hands of a skilled tradesman.”

As for the additional cost associated with the time and focus required, SHOTZ said, “Cheaper to calibrate and print once than to have a job rejected and print it twice.”

Bill Clarke, technical customer services for Circle Services (Southend on Sea, UK), summed up what, in the end, appeared to be the consensus of the group. “Every machine and technology has its faults. Even the same press from the same manufacturer will have differences; operators need to be skilled and trained to accept new concepts or points of view; conditions and materials have to be checked, ‘approved,’ and above all fit for purpose. There are no short cuts. My advice would be look at your market place, find out what is commercially acceptable in that arena, decide what quality you need to achieve to stand out from the crowd, ensure you have the right backup and support, and then hit the button and run.”

LinkedIn comments have been edited for grammatical accuracy and tightened for length.